1. Field of the Invention
The invention relates to maintenance interval monitor, especially those designed for use with motor vehicles.
2. Description of the Prior Art
The maintenance of a modern motor vehicle is very important because of the constantly increasing cost of a new vehicle and of any major repairs to the vehicle. Most major repairs on a motor vehicle can be eliminated or delayed by proper attention to a relatively small number of items. Properly maintaining these items extends the period between major repairs as well as extends the vehicle life. Therefore it is important that the vehicle owner be aware of the need to service these items.
Generally, the important items need maintenance at different, independent intervals. For this reason, it is difficult for the owner to keep track of which item needs maintenance at which interval.
Additionally, the maintenance intervals vary depending upon the vehicle's actual use. For example, oil must be changed frequently when the vehicle is used only for short trips, while more miles are acceptable between oil changes if the vehicle is used only for long distance, highway driving. This variability of usage further complicates the problem of vehicle maintenance, because generally manufacturer maintenance recommendations are for only a single milage value, thereby creating many non-optimal maintenance situations. For these reasons, a number of types of maintenance interval monitors have been proposed.
For example, U.S. Pat. No. 4,031,363 involved an electronic monitor which indicated the need for vehicle maintenance after a fixed time interval or after a fixed distance interval. The distance traveled was determined from the speedometer cable or other mileage sensor. The monitor did not allow the intervals to be changed by the vehicle owner.
U.S. Pat. No. 4,159,531 relates to an electronic service indication system. When queried, the system indicated the next mileage at which maintenance should be performed and the names of the tasks to be performed. The suggested mileages between tasks was not alterable by the user and there was no prompting to indicate when service was to be performed. The system also allowed storage of the actual mileages at which service was performed by the proper facility, but required special equipment to record the values.
In U.S. Pat. No. 4,307,291, a mechanical maintenance monitor with a series of rotatable wheels was driven by the vehicle's speedometer cable. An electrical circuit closed to indicate the set interval completion. A number of different intervals corresponding to different tasks could be set by the manufacturer, but the maintenance intervals were not adjustable by the owner.
U.S. Pat. No. 4,404,641 disclosed an electronic equipment maintenance monitor which compared elapsed running time with owner selectable time values to enable warning indicators and equipment disabling devices.
U.S. Pat. No. 4,739,482 disclosed an improved motor vehicle maintenance interval monitor which had three connections to the electrical system of the vehicle. One connection was to ground, one was to a positive voltage which was present at all times and the third connection was to a positive voltage present only when the vehicle was running. The monitor determined the running time of the vehicle and multiplied this by an assigned, estimated vehicle speed, so that an estimated distance was determined. This distance was subtracted from various maintenance item intervals to result in a countdown to zero, indicating that maintenance was due on that item. An alarm was employed when maintenance was required. Several maintenance items could be separately tracked.
One of the common problems of the above-mentioned prior art monitors was that they had to be installed in a vehicle by persons having electrical or wiring skills and mechanical assembly skills. This problem eliminated from consideration any monitors requiring electrical connections or mechanical connections to the vehicle speedometer cable. Because mileage is the common standard used to determine maintenance requirements, only monitors using miles for the service interval were really effective. This made undesirable monitors which measured only elapsed time. Most monitors had maintenance intervals settable only by the monitor manufacturer, which made them undesirable if the owner desired different maintenance intervals.